netfilter: use function typedefs for __rcu NAT helper hook pointers

After commit 07919126ecfc ("netfilter: annotate NAT helper hook pointers
with __rcu"), sparse can warn about type/address-space mismatches when
RCU-dereferencing NAT helper hook function pointers.

The hooks are __rcu-annotated and accessed via rcu_dereference(), but the
combination of complex function pointer declarators and the WRITE_ONCE()
machinery used by RCU_INIT_POINTER()/rcu_assign_pointer() can confuse
sparse and trigger false positives.

Introduce typedefs for the NAT helper function types, so __rcu applies to
a simple "fn_t __rcu *" pointer form. Also replace local typeof(hook)
variables with "fn_t *" to avoid propagating __rcu address space into
temporaries.

No functional change intended.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202603022359.3dGE9fwI-lkp@intel.com/
Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>

5 files changed, 41 insertions, 26 deletions

diff --git a/include/linux/netfilter/nf_conntrack_amanda.h b/include/linux/netfilter/nf_conntrack_amanda.h
index dfe89f38d1f7..1719987e8fd8 100644
--- a/include/linux/netfilter/nf_conntrack_amanda.h
+++ b/include/linux/netfilter/nf_conntrack_amanda.h
@@ -7,10 +7,13 @@
 #include <linux/skbuff.h>
 #include <net/netfilter/nf_conntrack_expect.h>
 
-extern unsigned int (__rcu *nf_nat_amanda_hook)(struct sk_buff *skb,
-					  enum ip_conntrack_info ctinfo,
-					  unsigned int protoff,
-					  unsigned int matchoff,
-					  unsigned int matchlen,
-					  struct nf_conntrack_expect *exp);
+typedef unsigned int
+nf_nat_amanda_hook_fn(struct sk_buff *skb,
+		      enum ip_conntrack_info ctinfo,
+		      unsigned int protoff,
+		      unsigned int matchoff,
+		      unsigned int matchlen,
+		      struct nf_conntrack_expect *exp);
+
+extern nf_nat_amanda_hook_fn __rcu *nf_nat_amanda_hook;
 #endif /* _NF_CONNTRACK_AMANDA_H */
diff --git a/include/linux/netfilter/nf_conntrack_ftp.h b/include/linux/netfilter/nf_conntrack_ftp.h
index f31292642035..7b62446ccec4 100644
--- a/include/linux/netfilter/nf_conntrack_ftp.h
+++ b/include/linux/netfilter/nf_conntrack_ftp.h
@@ -26,11 +26,14 @@ struct nf_ct_ftp_master {
 
 /* For NAT to hook in when we find a packet which describes what other
  * connection we should expect. */
-extern unsigned int (__rcu *nf_nat_ftp_hook)(struct sk_buff *skb,
-				       enum ip_conntrack_info ctinfo,
-				       enum nf_ct_ftp_type type,
-				       unsigned int protoff,
-				       unsigned int matchoff,
-				       unsigned int matchlen,
-				       struct nf_conntrack_expect *exp);
+typedef unsigned int
+nf_nat_ftp_hook_fn(struct sk_buff *skb,
+		   enum ip_conntrack_info ctinfo,
+		   enum nf_ct_ftp_type type,
+		   unsigned int protoff,
+		   unsigned int matchoff,
+		   unsigned int matchlen,
+		   struct nf_conntrack_expect *exp);
+
+extern nf_nat_ftp_hook_fn __rcu *nf_nat_ftp_hook;
 #endif /* _NF_CONNTRACK_FTP_H */
diff --git a/include/linux/netfilter/nf_conntrack_irc.h b/include/linux/netfilter/nf_conntrack_irc.h
index 4f3ca5621998..ce07250afb4e 100644
--- a/include/linux/netfilter/nf_conntrack_irc.h
+++ b/include/linux/netfilter/nf_conntrack_irc.h
@@ -8,11 +8,14 @@
 
 #define IRC_PORT	6667
 
-extern unsigned int (__rcu *nf_nat_irc_hook)(struct sk_buff *skb,
-				       enum ip_conntrack_info ctinfo,
-				       unsigned int protoff,
-				       unsigned int matchoff,
-				       unsigned int matchlen,
-				       struct nf_conntrack_expect *exp);
+typedef unsigned int
+nf_nat_irc_hook_fn(struct sk_buff *skb,
+		   enum ip_conntrack_info ctinfo,
+		   unsigned int protoff,
+		   unsigned int matchoff,
+		   unsigned int matchlen,
+		   struct nf_conntrack_expect *exp);
+
+extern nf_nat_irc_hook_fn __rcu *nf_nat_irc_hook;
 
 #endif /* _NF_CONNTRACK_IRC_H */
diff --git a/include/linux/netfilter/nf_conntrack_snmp.h b/include/linux/netfilter/nf_conntrack_snmp.h
index 99107e4f5234..bb39f04a9977 100644
--- a/include/linux/netfilter/nf_conntrack_snmp.h
+++ b/include/linux/netfilter/nf_conntrack_snmp.h
@@ -5,9 +5,12 @@
 #include <linux/netfilter.h>
 #include <linux/skbuff.h>
 
-extern int (__rcu *nf_nat_snmp_hook)(struct sk_buff *skb,
-				unsigned int protoff,
-				struct nf_conn *ct,
-				enum ip_conntrack_info ctinfo);
+typedef int
+nf_nat_snmp_hook_fn(struct sk_buff *skb,
+		    unsigned int protoff,
+		    struct nf_conn *ct,
+		    enum ip_conntrack_info ctinfo);
+
+extern nf_nat_snmp_hook_fn __rcu *nf_nat_snmp_hook;
 
 #endif /* _NF_CONNTRACK_SNMP_H */
diff --git a/include/linux/netfilter/nf_conntrack_tftp.h b/include/linux/netfilter/nf_conntrack_tftp.h
index 1490b68dd7d1..90b334bbce3c 100644
--- a/include/linux/netfilter/nf_conntrack_tftp.h
+++ b/include/linux/netfilter/nf_conntrack_tftp.h
@@ -19,8 +19,11 @@ struct tftphdr {
 #define TFTP_OPCODE_ACK		4
 #define TFTP_OPCODE_ERROR	5
 
-extern unsigned int (__rcu *nf_nat_tftp_hook)(struct sk_buff *skb,
-				        enum ip_conntrack_info ctinfo,
-				        struct nf_conntrack_expect *exp);
+typedef unsigned int
+nf_nat_tftp_hook_fn(struct sk_buff *skb,
+		    enum ip_conntrack_info ctinfo,
+		    struct nf_conntrack_expect *exp);
+
+extern nf_nat_tftp_hook_fn __rcu *nf_nat_tftp_hook;
 
 #endif /* _NF_CONNTRACK_TFTP_H */